Bifocal lens.



No. 839,998. PATENTED JAN. 1, 1907.

H. O. JOERDEN.

BIFOGAL LENS APPLIGATION FILED MAR.15,1$mB.

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HENRY'YC. JOKERDEN, on Mainline. MISSOURI.

BIFQCAL LENS.

Specification of Letters Patent.

Patented J 'an. 1,1907.

Application filed March 18, 1606. -$eria1 No. 305336;

To, all whom it may co'nc'erh; I 7 Be it known that I, HENRY G. JoERnEN, a' citizen of the United States, residingat Marling, in the county of Montgomery and State of Missouri, have invented a new and useful Bifocal Lens, of which the following is a specification; 1 V 7 This invention relates to bifocal lenses, and has for one of itsobjects to provide a lens -a smooth external surface in order to avoid irritating the eye or cutting the' lashes.

A further object of the invention is to pro-f vide a bifocal lehs which may be accurately made by an ordinary Optician with the litmost accuracy and at comparativelysniall cost.

. provide a bifocal lens having A still furtherobject of the invention is to a perfectly smooth exterior surface.

A still further object of the invention is to provide a bifocal lens having -a chromatic distant vision.

A still further object of the invention is to 1pirovide a bifocal lens that is clear-and free, oin cement or similar holding material in the line of either the distant or reading focus. With these and other objects in view, as

. will more fully hereinafter a pear,- the invention consists in certain nove featuresof construction and arran ement of parts, hereinafter fully described, illustrated in theaccompanying drawings, andparticularly pointed out in the appended claims, it being understood that various changes in the form, proportions, size, and minor details-of the structure may be made without departing from the spirit or sacrificing any of the advanta es of the invention.

n the accompanying drawings, Figure 1 is a sectional elevation, on an exaggerated scale, of a bifocal lens constructed in accord' ance with the invention. Fi 2 is a similar I View of the three lens mem ersjdetached.

, tion.

Fig. 3 is a face view of the outer lens. Fig. 4 is a similar view of the central lens. 1 Flg 5 1s a faceview of the inner lens. Fig. 6 Illustrates a slight modification of the construe? tion of the center lens. Figs. 8, 9, and 1G I are sectional views corresponding to,F1g. 1 and illustrating modifications of the inven- Similar numerals of reference are em ployed to indicate corresponding arts enter.

narrow slit 17.

throughout. the several figures he; rawg l r The lens forming the subject of -the invention is one of that'class employed for distant vision, and: for read1ng,and n carrying the invention into eifect three'separate'lenses-are formed;

ordinary purposes, such as The two outer lenses 10 and 11 are convex f and they may be biconvex or plane-convex:

and of any curvature desired in accordance:

with the refractive power called for in the--.-;-

rescri tion.

These ,two lenses are usuall orme of crown-glass, and between'th'em 1a placed a concave lens 12, which inaccordor plane-concave."

It is well known that where a concave' lens is placed adjacent to one or more conveiry lenses the refractive powerof the latter'is .ance with the refraction desired will moief or less concave and may be eitherbiconcavereduced and the centrallens is therefore so 11;.

ground that the focal distance of the entire ens may be altered as required for 'distant vision. At a point'at or near: the lower edge of the central lens is formed an opening 15," which 'rnafy be of the character shown in 4 or whic may be formedhs shown in 1 6. At the point where formed there is no subtractionof the ewe of the convex lenses 10-and 1, nd the atte'r may therefore be employed-for; reading or close "work when the line ,of vision'js' 'directed' through the opening.

As all of the. 'ortions around the. wall of the openin inc uda-the;

concaved or reducing lens, the ocallength is,

increased for distant V1S 10I1 eyes are raised or directed to one side of the opening. The three lenses are securedtdgether in the usual manner; but a small slit 17='is formedinthe lower portionof thecen:

whenever the tral lens in order to permit expulsion of'air as the lenses are forced together,s0 that'there will be no danger of subsequent edue to expansion of air in case the le By preference,.. theair withirflflie s formed by said opening'is withdrawn an the opening sealedat'the sl't 17, so that it roe comes mpossible for'air, dirt, or moisture to},

In the construction shown in the central-lens in place of forming t "e efuiai opening is continued down'to the lower ed a 0 =i Inasmuch 81813119 different as lengths are secured log difference-in the thickness of the lensat di erent points, it is obvious that fur thermodifications of the invention l it;

I made. One of these is illustrated in Fig. 7, wherein an ordinary form of plano-concave cated by the line lens 12 is provided with a recess-15, that is formed by grindmg in from the concaved side of the lens by a circular or other suitable form of grinder. The quantity of material removed from the concaved side of the lenswill depend altogether on the nature of the case under treatment.

illustrates, on an enlarged scale, the manner in which the grinding away of portions of the concaved lens may be accomlished. The ordinary form of lens is indiw and the lens in the majorityof cases will be ground out to the line m. 11 order to meet certain conditions of the eye, the grinding may be carried on to the po nt y to form a conoaved side at this point; To meet other conditions, the convex side z may be formed. Against this may be fitted a convex outer lens 10. .ifhe resultis a bifocal lens that is smooth and has uninterrupted outer faces. The invention may also be applied to periscgpic lenses of thetype shown,

for instance, in g. 8 wherein the concaved lens is ground out in order to decrease the refractive ower in the plane of the short or reading ocus. Fig. 9 illustrates a constructiOn in which a biconvex lens 10 and a biconcaved lens 12 are employed, and both of these are reduced in thickness to form a chamber 15.

The lens may be further modified without departing from the invention, which includes broadly all bifocal lenses in which the differ ence in focal len the is secured by altering the thickness of g ass for the different foci.

I claim- 4 1. Acompound bifocal lens including an incomplete member, the incomplete portion ceases lloeing protected by another member of the 2. A compound bifocal lens including an incomplete concave member, the incomplete portion being protected by another member ofthe lens.

3. A bifocal lens comprising a plurality of lens members, one of which is provided with an opening or recess, the opening being covered by another member of the lens.

4:. A compound bifocal lens comprising an intermediate incomplete concaved member and outer convex members.

5. A compound bifocal lens comprising outer convex members, and an intermediate concave member, a portion of which is cut away to decrease the focal distance of the lens for near vision.

6. A compound lens comprising outer members one of which is convex, and a central concaved member, the latter being provided with an opening at its lower central portion. 1

7. A compound lens including a central member having an opening forming a vacuum-chamber.

8. A compound lens including a central member having an opening, there being a slit extending from the opening to the edge of the lens to permit exhausting the air from the opening when the lens members are assembled.

In testimony that I claim the foregoing as my own I have hereto affixed my signature in the presence of twowitnesses.

HENRY C. JOERDEN Witnesses:

T. F. JONES, W. S. TRAINER. 

